Mitigation of Antimicrobial Resistance (AMR) in Water Resources: Risk, Mitigation, Guidance and Policy Updates

A notable contributor to pharmaceuticals in the environment (PiE) stems from patient medication use and subsequent excretion, along with other significant sources such as pharmaceutical manufacturing, non-point sources from livestock, and healthcare and solid waste facilities. This paper examines the impact of antibiotic discharge into surface water bodies from these various facilities, highlighting the potential emergence of antimicrobial resistance (AMR) at critical concentration levels. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) have recognized AMR as one of the foremost threats to human health. Research indicates that both natural and treated water environments play crucial roles in the evolution and dissemination of AMR. Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) can transfer between humans, animals, and the environment, complicating the treatment of certain infections. Recent global initiatives, including antimicrobial stewardship and AMR surveillance, have been launched to address this pressing issue. In support of WHO's initiatives, the AMR Industry Alliance (AMRIA) introduced a comprehensive framework for antibiotic manufacturing in 2022, advocating for a risk-based approach to managing manufacturing waste. Moreover, in 2024, WHO issued guidance recommending stricter concentration limits at source boundaries to mitigate excessive releases into water bodies. The directives target regulatory bodies, publicly owned treatment works (POTWs), antibiotic purchasers, pharmaceutical companies, healthcare providers, waste facilities, and pharmaceutical investors, with the European Union spearheading efforts to reduce PiE and AMR through forthcoming legislation. Wastewater treatment facilities represent significant potential receptors and sources for ARB and ARGs. These facilities process a mixture of pathogens, resistant genes, and antimicrobial drug residues from various origins, including industrial wastewater, households, and hospitals, leading to a high density of pathogens entering the plant. As treated wastewater is often discharged into aquatic environments, these areas become potential exposure routes for resistant pathogens and genes to humans and animals through irrigation, recreational activities, or drinking water. While drinking water treatment processes generally reduce ARB and ARGs effectively, traces of both have still been detected in treated drinking water. Given the rapid evolution of ARB and ARGs and their mobility between the environment, humans, and animals, predicting the timing and location of resistance emergence is challenging. More comprehensive data is required to characterize the prevalence and implications of AMR in treated municipal wastewater effluent and biosolids. Additionally, further research is essential to enhance understanding of AMR's impact on receiving waters and the associated risks of AMR in treated wastewater discharge, water reuse, and biosolids. In response to these needs, the EPA has allocated $9 million in research grants aimed at addressing knowledge gaps and improving the identification and management of antimicrobial resistance risks. Water scarcity and drought conditions are increasingly affecting various regions in Europe, a situation anticipated to worsen due to climate change. In 2012, the European Commission (EC) expressed its commitment to addressing water scarcity and promoting water reuse. Currently, the EC is focused on establishing minimum quality requirements for water reuse and evaluating the fate of emerging contaminants following irrigation with reclaimed wastewater. Pharmaceuticals are among the emerging contaminants that exhibit persistence and potential bioaccumulation across different environmental compartments, necessitating careful monitoring of their presence in treated wastewater. Similar challenges are faced by arid regions in the western United States, where rising water costs and the widening gap between global water supply and demand pose significant risks if current practices continue, particularly in pharmaceutical product development. In January 2025, US news outlets reported that researchers found wastewater treatment plants remove less than 25% of organo-fluorinated compounds, many of which originate from commonly prescribed medications. This issue is particularly critical during droughts when treated wastewater is reused as drinking water, potentially exposing up to 23 million individuals. This paper will provide an overview of the mechanisms underlying antibiotic resistance and conduct a thorough analysis of existing guidelines, incorporating hypothetical scenarios of antibiotic release from various sources, including residential, healthcare, manufacturing, waste management, and animal health non-point sources. In instances where projected concentrations surpass risk-based thresholds, a range of treatment technologies and considerations will be proposed for the effective mitigation of antibiotic molecules.